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US 5,672,201 AGranted
Composite pigmentary material
AssigneeTioxide Group Services Limited
InventorsLeslie Ainsley Simpson, Keith Robson, David Trevor Knight, Ronald Brown
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AssigneeTioxide Group Services Limited
InventorsLeslie Ainsley Simpson, Keith Robson, David Trevor Knight, Ronald Brown
Estimating the term…
A process for preparing a structured composite pigmentary material comprises forming a dispersion of uncoated particles of titanium dioxide at a pH value at which the particles have a surface charge and subjecting the dispersion to cross-flow filtration until the dispersion contains more than 50% by weight titanium dioxide. The concentrated dispersion is mixed with a dispersion of chemically distinct particles having a surface charge of opposite sign under conditions which ensure that the sign of the surface charge on either of the particulate materials is not reversed. In the resultant composite pigmentary material the titanium dioxide particles are held in association with the chemically distinct particles as a result of said surface charges. The structured composite can be used to produce paints having higher opacity than conventional paints containing an equivalent amount of titanium dioxide and the durability of these paints is better than a conventional paint containing a similar amount of uncoated titanium dioxide.
A process for the preparation of a structured composite pigmentary material comprising forming an aqueous dispersion of uncoated particles of pigmentary titanium dioxide, said dispersion having a pH value such that the particles of titanium dioxide have a surface charge, subjecting the dispersion to the effects of cross-flow filtration, continuing the cross-flow filtration until the dispersion contains more than 50 per cent by weight titanium dioxide and subsequently mixing said dispersion with a dispersion of chemically distinct particles having a surface charge of opposite sign to the charge on the titanium dioxide particles under conditions such that the mixing does not produce a reversal of the sign of the surface charge on one of the particulate materials, thereby forming a composite pigmentary material in which titanium dioxide particles are held in association with chemically distinct particles as a result of said surface charges.
Dependencies are inferred from the claim text.